Diehl was released by the Guardians on Wednesday.
Diehl has spent all of 2023 at Triple-A Columbus, where he posted a 6.89 ERA and 35:20 K:BB over 32.2 innings. The lefty has had gaudy strikeout totals at times in the minors but has managed just a 9.47 ERA and 15:6 K:BB over 19 frames at the major-league level.